Modulation of combustion rates in fuels

ABSTRACT

There is disclosed a fuel additive composition including at least one of: i) a particle(s) or nanoparticle(s) of oxide(s), hydroxide(s), hydrate(s), and/or carbonate(s) selected from the group consisting of: Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V; and ii) an alloy(s) or nanoalloy(s) containing two or more metals selected from the group consisting of Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V; wherein at least one of the i) particles or nanoparticles and ii) alloys or nanoalloys can be capped with at least one iii) flame retardant material. The fuel additive composition can modulate fuel combustion.

DESCRIPTION OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to an additive composition comprising atleast one of i) a metal-based particle and ii) an alloy, wherein atleast one of i) the particle and ii) the alloy is capped with at leastone iii) flame retardant material. By selecting the particular particleand/or alloy based upon its size, shape, and mass, one of ordinary skillin the art can modulate the combustion rate of the fuel.

2. Background of the Disclosure

Fuels are burned in different combustion systems to achieve a certaintask. How well the task is achieved depends on many factors, the primaryones being the design of the respective combustion system, and howefficiently the fuel burns to optimize the performance of thatcombustion system.

Efficient combustion of fuel depends on the fuel quality used. Byquality, it is implied how well suited the fuel is to the specificcombustion system, both in the short term efficiency, and long termdurability of the combustion system. Fuel quality is predominantly abulk feature of the fuel that is determined by how the fuel is sourced.However, because fuel sources are so variable, fuel additives play amajor role in leveling out this variability. More often than not, it ismore cost effective to correct a fuel's quality with appropriateadditives than through bulk fuel sourcing parameters.

In developing a fuel for combustion systems, the combustion rates areprimary considerations. Once the rates are achieved, control of thoserates is critical. When energetic functionalities are incorporated in afuel, then the primary concern is how to modulate the ensuing combustionevent by slowing it down to the desired rate. In most cases this ratehas to be shaped to meet changing requirements of the combustion system.If the fuel is solid, then combustion modulators for different rates canbe partitioned in the fuel bulk to impart their specific effect when thecombustion front reaches their location.

For example, a rocket's combustion and acceleration rate must beinitially curtailed to prevent excessive heat and its resulting possibledamage to the vessel. At a slightly later time or altitude, the rocket'scombustion rate can be increased by the diminution of the initialcombustion modulator or conversion to an alternative combustionmodulator.

Thus, a graph or ratio of the combustion rate compared to the thrustproduced by the combustion is different for rockets, missiles andprojectiles, such as shells and artillery. And characteristic fuelcombustion rates for each of these applications also vary as describedin the preceding paragraph. Tailoring the desired combustion rates foreach such application is currently problematic.

To slow or modulate combustion rates, additives capable of absorbingfree radicals can be necessary. Examples can be found in flame orcombustion retardants, also referred to herein as decelerants ormodulators. Another class is octane, or “anti-knock” additives for sparkignited engines, such as tetraethyl lead, methyl cyclopentadienylmanganese tricarbonyl (“MMT”), cyclopentadienyl manganese tricarbonyl(“CMT”), ferrocene, alcohols, arylamines, etc. Metallic anti-knockadditives are far superior to organics and require orders of magnitudeless additive than the organics to achieve the same task. Metallics areadded in ppm levels to the fuel whereas organics are in percent amounts.

The physical form of metal-containing additives of most recent interestis the nanoparticle form because of its unique surface to volume ratiosand active site numbers and shapes. As is to be expected, there isinterest in mixed metal nanoadditves because each metal tends to havespecific functions. Therefore, what is needed is an additive compositionthat can be formulated to modulate fuel combustion rates.

SUMMARY OF THE DISCLOSURE

In accordance with the disclosure, there is disclosed hereinnanoparticle and nanoalloy compositions of fuel combustion modulators,and methods of applying these modulators to different combustion systemsto optimize desired efficiencies.

In an aspect, there is disclosed a fuel additive comprising at least oneof: i) a particle(s) or nanoparticle(s) of oxide(s), hydroxide(s),hydrate(s), and/or carbonate(s) selected from the group consisting of:Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd,Co, Ni, Cr, Ti, Ce, and V; and ii) an alloy(s) or nanoalloy(s)containing two or more metals selected from the group consisting of Al,Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co,Ni, Cr, Ti, Ce, and V; wherein at least one of the i) particles ornanoparticles and ii) alloys or nanoalloys can be capped with at leastone iii) flame retardant material.

DESCRIPTION OF THE DISCLOSURE

The present disclosure relates to a fuel additive composition comprisingat least one of i) a metal-based particle and ii) an alloy, wherein atleast one of i) the particle and ii) the alloy is capped with at leastone iii) flame retardant material. By selecting the particular particleand/or alloy based upon its size, shape, and mass, one of ordinary skillin the art can modulate the combustion rate of the fuel. In particular,one can modulate fuel combustion rates, such as a solid fuel, byformulating the additive composition with the appropriate additized fueland combustion modulator in particles and/or alloy compounds.

The current use of metals in combustion systems relies on chemistriesfostered by each metal type as dictated by its unique orbital andelectronic configuration acting individually. This means that inadditives formulated with metal mixtures, at the time of the intendedactivity, the metals act independently from one another during fuelcombustion. In fact, the physics of a combusting charge minimizes thelikelihood that a mixed metal additive will locate the different metalatoms within the same and/or desired and/or proper and/or preferredlocation on the combusting fuel species so that they may act in unisonas a single entity.

Combustion modulators disclosed herein can be designed to do this basedon: i) metal-based particle, and/or, ii) alloy, and/or, iii) flameretardant material. The core particle or alloy can be fined tunedfurther to achieve desired modulation rates by size and shape design bythe use of an organic capping ligand with a polar heteroatom derivedfunctionality, such as nitrogen (N), phosphorus (P), and otherheteroatoms giving rise to polar functional groups, with all polarfunctional groups collectively designated as “X”. The capping ligandwould then be used to provide the final polishing to the additiveperformance.

In an aspect, the additive composition can comprise at least one of:

-   -   i) a particle(s) or nanoparticle(s) of oxide(s), hydroxide(s),        hydrate(s), and/or carbonate(s) selected from the group        consisting of: Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K,        Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V; and    -   ii) an alloy(s) or nanoalloy(s) containing two or more metals        selected from the group consisting of Al, Sb, Mg, Fe, Mo, Zn,        Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti,        Ce, and V;

wherein at least one of the i) particles or nanoparticies and ii) alloysor nanoalloys can be capped with at least one iii) flame retardantmaterial. The flame retardant material can be selected from the groupconsisting of polyhalogenated alkyl halides, polyhalogenated arylhalides; alkyl phosphorus-derived oxides, aryl-phosphorus-derivedoxides; and ammonia, alkyl amines, and aryl amine.

In an aspect, the i) particle(s) or nanoparticle(s) can be, for example,hydroxides, such as Mg(OH)₂, Ti(OH)₂, etc.; metal oxides, such as Sb₂O₃,SnO₂, ZnO, MoO₃, Fe₂O₃, CoO, (NH₄)₄Mo₈O₂₆, etc.; hydrates, such asAl₂O₃.3H₂O, Al(OH)₃(H₂O)_(x), etc.; and carbonates, such as CaCO₃,MgCO₃, etc.

In another aspect, the ii) alloy(s) or nanoalloy(s) can be, for example,Al/Sb, Na/B, Zn/B, Na/Sb, Fe/Mn; borates, borate/hydrates, andborate/hydrate/oxides, such as Ba(BO₂)₂, LiB₃O₅, 2ZnO.3H₂BO₃.3.5H₂O,Na₂B₄O₇.10H₂O, etc.; and antimonates, such as Na₃SbO₄, LnSbO₄, SiSbO₄,FeSbO₄, TiSbO₄, CeSbO₄, VSbO₄, VMoSbO₄, MnVSbO₆, CaMnSb₄O₁₄, BaSbO₅,Ca₂O.SbO₅, Co₂O.Sb₂O₅, Mg₂O.Sb₂O₄, etc.

In another aspect, the at least one iii) flame retardant material can bea ligand to give compositions “i(R—X_(m))_(n)” and/or “ii(R—X_(m))_(n)”,where:

i) and ii) are as defined above;

—R—X_(m) is a functionalized organic moiety with a polar functionalgroup “X” (i.e. phosphite, phosphate, phosphonate, phosphate esters,carboxylate, alkoxylate, halogenate, amine, etc) that can have flameretardant capability and can also enable R—X to function as a cappingligand to prevent agglomerization of (i) and/or (ii);

R is an organic moiety (i.e. alkyl substituted -cyclopentadienyl,-phenyl, -naphthyl, -anthracyl, -alkyl, -alkenyl etc., wherein the alkylsubstituent ranges from C1 to C32 carbon length, the actual length beingthe minimum necessary to impart the respective fuel compatibility to theadditive; and

when X is bromine and R contains aromatic rings, then “m” is an integerthat ensures perbromination of the aromatic rings in a similar manner toconventional brominated flame retardants, and

“n” is the number of R—X_(m) ligands necessary to stabilize i) and ii),and is greater than 0, such as from 15-20;

“m” is an integer greater than 1.

In particular, the additive composition could comprise a particle ofcerium oxide that has been treated with an alkyl amine and an alloy ofSb_(x)Zn_(y)B_(z) or Al_(x)Sb_(y)Zn_(z) that has been treated with apolyhalogenated alkyl halide and an alkyl phosphorus-derived oxide,where x, y and z are independent integers or decimal fractions.

Examples of other embodiments of the present disclosure include:

iv=“i” combinations with alkyl- or aryl-phosphorus-derived oxides

v=“ii” combinations with alkyl- and/or aryl-phosphorus-derived oxides

vi=“iv” combinations with ammonia and/or alkyl- and or aryl-amines

vii=“ii” combinations with polyhalogenated alkyl- and/or aryl-halides

viii=“ii” combinations with alkyl- and/or aryl-phosphorus-derived oxides

ix=“vii” combinations with alkyl- and/or aryl-phosphorus-derived oxides

x=“vii” combinations with ammonia and/or alkyl- and/or aryl-amines,and/or polyamines.

Methods of combustion modulation useful herein include, a) fuel dilutionby generation of non-combustible gases, such as, N₂, H₂O, CO₂, HX(X=halogens), SO₃, etc., b) cooling endothermic reactions, c) formationof protective layer such as the production of metal oxide coatings, d)condensed phase activity (i.e. charring and cross-linking), e) vapor orgas phase activity (i.e. HX, HX/Sb, P, etc), and f) for metals, themodulation method is by free radical scavenging controls.

Fuel combustion can be modulated by, for example, by fuel dilutionthrough non-combustible gas generation such as N₂, HX, CO₂, SO₃, etc. asdemonstrated by the reactions:

a. Al₂O₃•3H₂O + heat → Al₂O₃(s) + 3H₂O(g) 230° C. b. Mg(OH)₂ + heat →MgO(s) + H₂O(g) 340° C. c. CaCO₃ + heat → CaO(s) + CO₂(g) 825° C. d.2ZnO•3H₂BO₃•3.5H₂O + heat → 2ZnO•3B₂O₃ + 290° C. 3.5H₂O(g) e.Na₂B₄O₇•10H₂O + heat → Na₂B₄O₇(s) + 10H₂O  65° C. f. 2Sb₂O₃ + 6HX heat →2SbX₃(g) + 3H₂O(g) g. SnO₂ + 4HX → SnX₄(g) + 2H₂O(g) h. bistetrazoles,bistetrazoleamines, dihydrazinotetrazines, bistetrazolylaminotetrazines,etc on combustion evolve gaseous nitrogen.In particular, provided herein is a method of modulating fuel combustionby producing fuel dilution by generation of non-combustible gasesselected from the group consisting of N₂, H₂O, CO₂, HX, and SO₃ saidmethod comprising: a) combining a fuel and a fuel additive as disclosedherein to form a mixture, wherein the additive comprises a materialcapable of generating, when heated, a non-combustible gas selected fromthe group consisting of N₂, H₂O, CO₂, HX, and SO₃; b) combusting themixture, thereby generating said non-combustible gas, whereby the fuelin said mixture is diluted.

Moreover, fuel combustion can be modulated by, for example, by coolingendothermic decomposition reactions:

i. Al₂O₃•3H₂O + heat → Al₂O₃(s) + 2H₂O(g) ΔH = −280 cal/g j. Mg(OH)₂ +heat → MgO(s) + H₂O(g) ΔH = −328 cal/gThus, there is provided herein a method of modulating fuel combustion byproducing cooling endothermic reactions, the method comprising:combusting a mixture of fuel and fuel additive as disclosed herein,whereby the fuel additive when heated enters an endothermic reaction,whereby cooling of the fuel combustion occurs.

In addition, fuel composition can be modulated by, for example, forminga protective glassy layer on a fuel:

-   -   k. phosphorous from phosphate esters and aryl-phosphorus derived        oxide nanoparticle/nanoalloy ligands etc and/or,    -   l. nitrogen from amines, and polynitrogenated sections of        ligands —R-Xm such as bistetrazoles, bistetrazoleamines,        dihydrazinotetrazines, bistetrazolylaminotetrazines, etc,        and/or,    -   m. silicon from silicon-containing nanoparticles/nanoalloys such        as SiSbO₄, and/or    -   n. boron from borated nanoparticles/nanoalloys such as Ba(BO₂)₂,        LiB₃O₅, 2ZnO.3H₂BO₃.3.5H₂O, Na₂B₄O₇.10H₂O, etc, and/or    -   o. zinc from zinc-containing nanoparticle/nanoalloy additives        with features such as 2ZnO.3H₂BO₃.3.5H₂O, etc.        By “protective glassy layer” herein is meant a layer or coating        of glass-like or ceramic-like material effective in retarding,        quenching extinguishing, and/or preventing further oxidation or        combustion of the fuel. Thus, there is provided herein a method        of modulating fuel combustion by forming a protective layer on a        solid fuel, said method comprising: a) combining a solid fuel        and a fuel additive as disclosed herein to form a mixture, b)        heating the mixture to a temperature at least sufficient to        cause the additive to form a protective glassy layer on the        mixture, whereby the fuel combustion is modulated.

In another aspect, fuel combustion can be modulated by, for example,condensed phase activity, such as charring and cross linking:

-   -   p. From nanoparticle/nanoalloy additives with P, N, metals, B,        S, Si, Bi, MO, MX, (M=metal and X+halogen) either individually        or in combination thereof. Examples of this kind are MoO₃,        BiCO₃, and (NH₄)₄Mo₈O₂₆ which perform the dual function of        combustion modulation and smoke suppression.        Thus, there is provided herein a method of modulating fuel        combustion by condensed phase activity, said method comprising:        combusting a mixture of fuel and fuel additive as disclosed        herein, whereby the fuel additive when heated induces phase        activity, such as charring and crosslinking, whereby the fuel        combustion is modulated. Further, there is provided herein a        method of smoke suppression by condensed phase activity, said        method comprising: combusting a mixture of fuel and fuel        additive as disclosed herein, whereby the fuel additive when        heated induces phase activity, such as charring and        crosslinking, whereby generation of smoke from said combustion        is suppressed.

In further aspect, fuel composition can be modulated by, for example,vapor or gas phase activity:

-   -   q. Additive compounds containing: arylamines, alcohols, Sb, HX,        HX/Sb, P (i.e. from phosphene oxides and phosphites.    -   r. Additive compounds containing metal complexes such as        tetraethyl lead, methyl cyclopentadienyl manganese tricarbonyl        (“MMT”), cyclopentadienyl manganese tricarbonyl (“CMT”),        ferrocene, SbCl₃, POCl₃, Pb(C₂H₅)₄, Fe(CO)₅, TiX, and mixtures        thereof.    -   s. Additive compounds with volatile Mn, Cr, Sn, and U moieties        are active in ppm levels in combustion modulation.        Thus, there is provided herein a method of modulating fuel        combustion by vapor or gas phase activity, said method        comprising: combusting a mixture of fuel and fuel additive as        disclosed herein, whereby the fuel additive when heated induces        gas phase activity, whereby the fuel combustion is modulated.

It is envisioned that the disclosed additive composition could cover alldifferent local flame modulation mechanisms. As previously disclosed,modulation of the combustion rates can be achieved by appropriatelyselecting particles and/or alloys based upon their mass, shape, andsize. However, mass, shape, and size are not limiting factors and allvariations of these parameters are contemplated for use in the disclosedadditive composition. For example, the particle and/or alloy may beformulated in a layered configuration with two different types ofcompounds, so that the outer surface would combust at a rate that isdifferent from an inner core. Similarly, different additive compositionsof this nature may be segregated and stratified in the matrix of a solidfuel such that different combustion modulation rates are sequentiallytriggered as the fuel burns. Moreover, the particle and/or alloy may beformulated in a particular shape, such as a platelet shape, because thisshape provides more active combustion areas through increased surfacearea as compared to a rod. Further, the particle and/or alloy may bechosen because it is more or less dense and consequently more or lessporous.

In an aspect, the additive composition can be formulated so that itprovides any desired color flame signature on combustion, which can beparticularly useful in flares and fireworks. Furthermore, poly-nitrogenring structures (such as for example, bistetrazoles and tetrazines)modulate fuel combustion by releasing gaseous nitrogen to slowcombustion. These can also impart color to the flame in cases where avisible exhaust signature is desired. These compounds can either bephysically mixed with nanoalloy combustion modulators of thisdisclosure, or be modified to serve a second function of “cappingagents” added during nanoalloy syntheses to control particle size. Tobecome capping agents that are also fuel dispersible, a hydrocarbonsolubilizing alkyl group of appropriate size (i.e. pentyl, hexyl,octadecanyl, etc) has to be grafted onto these polar hetero-nitrogenatedring structures.

Some examples include:

The metal-based particle and/or alloy compound for use in the disclosedadditive composition can be generated either in aqueous media, ororganic media.

In an aspect, the particles and/or alloys can, optionally, be coatedwith an organic capping ligand with a polar heteroatom-derivedfunctionality, such as nitrogen (N), phosphorus (P), and otherheteroatoms giving rise to polar functional groups, with all polarfunctional groups collectively designated as “X”; or otherwise treatedwith suitable hydrocarbon molecules that render them fuel soluble and/orto prevent agglomeration. For this purpose, they can be comminuted in anorganic solvent in the presence of a coating/capping agent which is anorganic acid, anhydride or ester or a Lewis base. It has been foundthat, in this way which involves coating in situ, it is possible tosignificantly improve the coating of the particle and/or alloy. Further,the resulting combustion modulation product can, in many instances, beused directly without any intermediate step. Thus in some coatingprocedures it is necessary to dry the coated particle and/or alloybefore dispersing it in a hydrocarbon solvent.

The coating agent can suitably be an organic acid, anhydride or ester ora Lewis base. The coating agent can be, for example, an organiccarboxylic acid or an anhydride, typically one possessing at least about5 carbon atoms, for example about 10 to about 30 carbon atoms, forexample from about 12 to 18 carbon atoms, such as stearic acid. It willbe appreciated that the carbon chain can be saturated or unsaturated,for example ethylenically unsaturated as in oleic acid. Similar commentsapply to the anhydrides which can be used. An exemplary anhydride isdodecylsuccinic anhydride. Other organic acids, anhydrides and esterswhich can be used in the process of the present disclosure include thosederived from phosphoric acid and sulphonic acid. The esters aretypically aliphatic esters, for example alkyl esters where both the acidand ester parts have from about 4 to about 18 carbon atoms.

Also useful herein as capping agents are the poly-nitrogen moleculesdescribed hereinabove and their alkylated derivatives, and otherhydrocarbons having a nitrogen-containing polar head group.

Other coating or capping agents which can be used include Lewis baseswhich possess an aliphatic chain of at least about 5 carbon atomsincluding mercapto compounds, phosphines, phosphine oxides and amines aswell as long chain ethers, diols, esters and aldehydes. Polymericmaterials including dendrimers can also be used provided that theypossess a hydrophobic chain of at least about 5 carbon atoms and one ormore Lewis base groups, as well as mixtures of two or more such acidsand/or Lewis bases.

When the additive is to be used in a combustor where the combustionbyproducts can attack and destroy the combustor's lining, then thecapping or coating agent can in one embodiment be a phosphoruscontaining ligand.

The coating process can be carried out in an organic solvent. Forexample, the solvent is non-polar and is also, for example,non-hydrophilic. It can be an aliphatic or an aromatic solvent. Typicalexamples include toluene, xylene, petrol, diesel fuel, jet fuels,vegetable and/or animal oils, fish oils, as well as heavier fuel oils.Naturally, the organic solvent used should be selected so that it iscompatible with the intended end use of the coated particle and/oralloy. The presence of water should be avoided, the use of an anhydrideas a coating agent helps to eliminate any water present.

The coating process involves comminuting the alloy so as to prevent anyagglomerates from forming. The technique employed should be chosen sothat the alloys are adequately wetted by the coating agent and a degreeof pressure or shear is desirable. Techniques which can be used for thispurpose include high-speed stirring (e.g. at least 500 rpm) or tumbling,the use of a colloid mill, ultrasonics or ball milling. Typically, ballmilling can be carried out in a pot where the larger the pot the largerthe balls. By way of example, ceramic balls of 7 to 10 mm diameter aresuitable when the milling takes place in a 1.25 liter pot. The timerequired will of course, be dependent on the nature of the alloy but,generally, at least 4 hours is required. Good results can generally beobtained after 24 hours so that the typical time is from about 12 toabout 36 hours.

The additive composition of the present disclosure can comprise at leastone alloy of two or more metals. As described herein, the alloy isdifferent chemically from any of its constituent metals because it showsa different spectrum in the X-ray diffraction (XRD) than that of theindividual constituent metals. In other words, it is not a mixture ofdifferent metals, but rather, an alloy of the constituent metals used.

The primary determining factors for activities metals is primarily thetype, shape, size, electronic configuration, and energy levels of lowestunoccupied molecular orbitals (LUMO) and highest occupied molecularorbitals (HOMO) made available by the metal to interact with those ofthe intended substrate species at conditions when these species are tobe chemically and physically transformed. These LUMO/HOMO electronicconfigurations are unique to every metal, hence the innatephysics/chemistry uniqueness observed between, for example, Mn and Pt,or Mn and Al, etc.

The disclosed alloy is the result of combining the different constituentmetal atoms in the compound. This means that the LUMO/HOMO orbitals ofthe alloy are hybrids of those characteristic of the respectivedifferent metal atoms. Therefore, an alloy ensures that all constituentmetals in the alloy particle end up at the same site and act as one, butin the modified i.e., alloy, form. The advantages of an alloy for thispurpose would be due to unique modifications imparted to the LUMO/HOMOelectronic and orbital configurations of the particles by the mixing ofLUMO/HOMO orbitals of the different respective alloy composite metals.The number and shape of active sites would be expected to also changesignificantly in the alloy composites relative to the number and shapeof active sites in equivalent but non-alloy mixtures. This uniqueorbital and electronic mixing at the LUMO/HOMO orbital level in thealloys is not possible by simply mixing particles of the respectivemetals in appropriate functional ratios.

An exemplary alloy can be represented by the following generic formula(A_(a))_(n)(B_(b))_(n)(C_(c))_(n)(D_(d))_(n)(E_(e))_(n)( . . . )_(n);wherein each capital letter and ( . . . ) is a metal describedhereinabove; wherein each n is independently greater than or equal tozero; and wherein the alloy comprises at least two different metals.Thus, the sum of the n's is equal to or greater than 2. In an aspect,the ( . . . ) is understood to include the presence of at least onemetal other than those defined by A, B, C and D and the respectivecompositional stoichiometry.

The metal for use in the alloy can also be selected from the groupconsisting of Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn,Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V. In an aspect, in the genericformula, each capital letter can be the same or a different metal.

Sources of the metal can include, but are not limited to, their aqueoussalts, carbonyls, oxides, organometallics, and zerovalent metal powders.The aqueous salts can comprise, for example, hydroxides, nitrates,acetates, acetonates, ammonium salts, halides, phosphates, phosphonates,phosphites, sulfates, sulfonates, carboxylates, and carbonates.

The subscript letters of the disclosed generic formula representcompositional stoichiometries. For example, for an A_(a)B_(b)C_(c)alloy, such as Fe_(0.68)Al_(0.25)Ce_(0.07) disclosed herein, a=0.68,b=0.25 and c=0.07.

In an aspect, the alloy can be a nanoalloy and can be bimetallic (i.e.,any combination of two different metals from the same or differentfunctional groups, e.g., A_(a)B_(b), or A_(a)A′_(a′)); trimetallic(i.e., any combination of three different metals from the same ordifferent functional groups, e.g., A_(a)B_(b)C_(c), orA_(a)A′_(a′)A″_(a″) or A_(a)A′_(a′)B_(b)); or polymetallic (i.e., anycombination of two or more metals from the same or different functionalgroups, e.g., A_(a)B_(b)C_(c)D_(d)E_(e) . . . etc. orA_(a)B_(b)B′_(b′)C_(c)D_(d)D′_(d′)E_(e)). The alloy must comprise atleast two different metals, but beyond two the number of metals in eachalloy would be dictated by the requirements of each specific combustionsystem.

In an aspect, the composition can comprise an alloy selected from thegroup consisting of a bimetallic, trimetallic, and polymetallic.

In an aspect, the disclosed alloy and particle can be a nanoalloy and ananoparticle. The nanoalloy and nanoparticle can have an average size offrom about 1 to about 100 nanometers, for example, from about 5 to about75 nanometers, and as a further example from about 10 to about 35nanometers.

One of ordinary skill in the art would know how to make the disclosedalloys. In particular, the disclosure of U.S. patent application Ser.No. 11/620,773, filed Jan. 8, 2007, the disclosure of which is herebyincorporated by reference.

Manipulation of reaction conditions will determine rate of reactionwhich will also determine the physical composition of the nanoalloy. Forexample, fast reaction rates will lead to low density and porousnanoalloys, and slow reaction rates to a denser and less porous product.This reduced surface area will adversely affect gas phase combustion,combustion emissions removal (i.e., SO₃ and NO_(x) from flue gases ofutility boilers and incinerator furnaces), and deposit modification(slag in furnaces). Such higher density nanoalloys will find enhancedutility in ceramics. Porous nanoalloys will find enhanced utility inatmosphere combustion systems, while denser nanoalloys will be bettersuited for pressurized combustion systems. Such porous nanoalloys aredescribed in Optical Materials, Tsui, Y. Y.; Sun, Y. W., Vol. 29, Issue8, pp. 1111-1114 (April 2007).

It is believed that the disclosed alloys can enable active metal speciesto function cooperatively due to their intimate location together infunctional units, such as nano units. The surface and the porosity ofthe alloy can be modulated by using nanotechnology methods ofpreparation known to those of ordinary skill in the art.

Also, disclosed herein is a fuel composition comprising a fuel and thedisclosed additive composition. The fuel can be a solid, liquid, or gas.By “solid fuel” herein is meant, for example and without limitationherein, materials useful as explosives, propellants, munitions, and thelike which can be produced in or changed to a solid form. Some examplesof these include, but are not limited, to nitrated cellulose, which canalso be melted to a liquid form. Other mononitrated, dinitrated,trinitrated and polynitrated materials can be used singularly or inadmixture as fuels herein. Nitrated aromatic materials and nitratedpolyaromatics are also useful herein. Other materials capable ofexplosion or detonation and which can in some manner or under somecondition be provided in solid form are also useful herein. These mightinclude, for example, epoxides, or epoxidized organic compounds,hydrides, metal hydrides, hydrazine and alkylated hydrazines, blackpowder propellant, zinc-sulfur, potassium nitrate, nitro glycerin,ammonium perchlorate, gun powder, and the like, and mixtures thereof,and other explosives or propellants known to those skilled in the art.

Moreover, the fuel can be a hydrocarbonaceous fuel such as, but notlimited to, diesel fuel, jet fuel, alcohols, ethers, kerosene, lowsulfur fuels, synthetic fuels, such as Fischer-Tropsch fuels, liquidpetroleum gas, bunker oils, gas to liquid (GTL) fuels, coal to liquid(CTL) fuels, biomass to liquid (BTL) fuels, high asphaltene fuels,petcoke, fuels derived from coal (natural and cleaned), geneticallyengineered biofuels and crops and extracts therefrom, natural gas,propane, butane, unleaded motor and aviation gasolines, and so-calledreformulated gasolines which typically contain both hydrocarbons of thegasoline boiling range and fuel-soluble oxygenated blending agents, suchas alcohols, ethers and other suitable oxygen-containing organiccompounds. Oxygenates suitable for use in the fuels of the presentdisclosure include methanol, ethanol, isopropanol, t-butanol, mixedalcohols, methyl tertiary butyl ether, tertiary amyl methyl ether, ethyltertiary butyl ether and mixed ethers. Oxygenates, when used, willnormally be present in the reformulated gasoline fuel in an amount belowabout 25% by volume, and for example in an amount that provides anoxygen content in the overall fuel in the range of about 0.5 to about 5percent by weight. “Hydrocarbonaceous fuel” or “fuel” herein shall alsomean waste or used engine or motor oils which may or may not containmolybdenum, gasoline, bunker fuel, coal (dust or slurry), crude oil,refinery “bottoms” and by-products, crude oil extracts, hazardouswastes, yard trimmings and waste, wood chips and saw dust, agriculturalwaste, fodder, silage, plastics and other organic waste and/orby-products, and mixtures thereof and emulsions, suspensions, anddispersions thereof in water, alcohol, or other carrier fluids. By“diesel fuel” herein is meant one or more fuels selected from the groupconsisting of diesel fuel, biodiesel, biodiesel-derived fuel, syntheticdiesel and mixtures thereof. In an aspect, the hydrocarbonaceous fuel issubstantially sulfur-free, by which is meant a sulfur content not toexceed on average about 30 ppm of the fuel.

In an aspect, the additive composition can be cold blended with thefuel, such as a solid fuel, at a treat rate of greater than 3 partsnanoparticles or nanoalloy per million parts (ppm) of solid fuel. Inanother embodiment, the treat rate can vary from about 5 ppm to about25,000 ppm, for example from about 5ppm to about 500 ppm, and as afurther example from about 100 ppm to about 500 ppm of solid fuel.

The alloys and particles disclosed herein can be formulated intoadditive compositions that can be in any form, including but not limitedto, gels, colloids, aerogels, paste, semi-solid, crystalline (powder),or liquids (aqueous solutions, hydrocarbon solutions, sols, oremulsions). The liquids can possess the property of being transformableinto water/hydrocarbon emulsions using suitable solvents andemulsifier/surfactant combination. The liquids can also be convertedinto high porosity high surface area powders.

The present disclosure, in another embodiment, is directed to combustionsystems generally. Combustion systems can have multiple sectionsincluding, in very general terms, a furnace, a combustion or ignitionsection, and an emissions after-treatment system. Combustion systemsthat require solid fuels include certain coal burning power utilityfurnaces, flares, fireworks, munitions, and the like. Combustion systemsthat burn gaseous, liquid, solid fuels, and renewable fuels, and mixturethereof include, but are not limited to, three-way catalysts (TWCs),such as for stoichiometric charge feed combustion systems, lean-NO_(x)traps (LNTs), lean-NO_(x) catalysts (LNCs), selective catalyticreduction catalysts (SCRs), such as for lean-burn variable pressureengines (i.e., diesel engines, lean-burn spark ignited engines, etc.),oxidation catalysts (OCs), diesel oxidation catalysts (DOCs), industrialburners in boilers, incinerators, furnaces, and lean-burn atmosphericburners (i.e., utility furnaces, industrial furnaces, boilers, andincinerators). As used herein, the term “after-treatment system” is usedto mean any system, device, method, or combination thereof that acts onthe exhaust stream or emissions resulting from the combustion ofgaseous, liquid, and solid fuels, renewable fuels, and mixtures thereof.

The disclosed additive composition can also be used in other systems,such as those of atmospheric combustion used in utility and industrialburners, boilers, furnaces, and incinerators. These systems can burnfrom natural gas to liquid fuels (#5 fuel oil and heavier), to solidfuels (coals, wood chips, burnable solid wastes, etc).

It is to be understood that the reactants and components referred to bychemical name anywhere in the specification or claims hereof, whetherreferred to in the singular or plural, are identified as they existprior to coming into contact with another substance referred to bychemical name or chemical type (e.g., base fuel, solvent, etc.). Itmatters not what chemical changes, transformations and/or reactions, ifany, take place in the resulting mixture or solution or reaction mediumas such changes, transformations and/or reactions are the natural resultof bringing the specified reactants and/or components together under theconditions called for pursuant to this disclosure. Thus, the reactantsand components are identified as ingredients to be brought togethereither in performing a desired chemical reaction (such as formation ofthe organometallic compound) or in forming a desired composition (suchas a washcoat composition). Accordingly, even though the claimshereinafter may refer to substances, components and/or ingredients inthe present tense (“comprises”, “is”, etc.), the reference is to thesubstance, components or ingredient as it existed at the time justbefore it was first blended or mixed with one or more other substances,components and/or ingredients in accordance with the present disclosure.The fact that the substance, components or ingredient may have lost itsoriginal identity through a chemical reaction or transformation duringthe course of such blending or mixing operations or immediatelythereafter is thus wholly immaterial for an accurate understanding andappreciation of this disclosure and the claims thereof.

The following examples further illustrate aspects of the presentdisclosure but do not limit the present disclosure.

EXAMPLE 1 Production of CeO₂ Nanoparticies

The following procedure was used to produce cerium oxide nanoparticleshaving a particle size of less than 5 nanometers. Cerium acetate (1gram, 0.00315 mols) was mixed with 7.5 mL of oleylamine (0.2279 mols)and 4.33 mL of oleic acid (0.13 mols) in a suitable vessel. The mixturewas heated to 110° C. and held at that temperature for 10 minutes toprovide a clear solution of cerium acetate without crystalline water inthe solution. Next, the cerium acetate solution was irradiated withmicrowave irradiation for 10 to 15 minutes to produce a stabledispersion of cerium oxide in the amine and acid. The stabilizeddispersion was washed 2-3 times with ethanol to remove any free amine oracid remaining in the dispersion. Finally, the stabilized cerium oxideproduct was dried overnight under a vacuum to provide the particles havea size of less than 5 nanometers. X-ray diffraction confirmed thatnanoparticles of crystalline cerium oxide were produced. UV absorptionof the product showed a peak at 300 nanometers which from extrapolationof the absorption edge indicated a band gap of 3.6 eV confirming thatthe nanoparticles have a diameter of less than 5 nanometers.

EXAMPLE 2 Production of Mg_(0.3)Mn_(0.7)O Nanoalloy Particles(Cubes+Spheres)

The following procedure was used to produce an alloy of magnesium andmanganese oxide nanoparticles. Oleylamine (4.25 mL, 0.129 mols) and 1.36mL of oleic acid (0.04 mols) was mixed in a suitable vessel that wasstirred and heated in a hot oil bath to 120° C. and held at thattemperature for 10 minutes. A mixture of magnesium acetate (0.14 grams)and manganese acetyl acetonate (0.34 grams) powder was added undervigorous stirring to the amine and acid to provide a clear solution. Thesolution was then microwaved for 15 minutes. After microwaving thesolution, synthesized nanoparticles of magnesium/manganese oxide wereflocculated with ethanol, centrifuged, and redispersed in toluene. TheMg_(0.3)Mn_(0.7)O nanoparticles made by the foregoing process have anx-ray diffraction pattern that indicates that traces of manganese oxideare included in the Mg_(0.3)Mn_(0.7)O alloy. The nanoparticles havecube-like structures similar to manganese oxide particles.

EXAMPLE 3 Preparation of Single Metal Flame Modulation Additive (FMA)Concentrate

Preparation of a metallic or metallic/metalloid nanoparticle ornanoalloy additive core, can be carried out using any of the publishedprep methods that are deemed suitable. Particle size control can beachieved by selection of suitable blends of a fatty amine or carboxylicacid. Then the core nanoparticle or nanoalloy can be coated with a flameretardant ligand —R(X)_(m) to give a neat FMA.

Na₃PO₄.12H₂O+-nR(X)_(m)→Na₃PO₄.12H₂O[—R(X)_(m)]_(n)

Where R(X)_(m) is a diaryl alkyl- or aryl-phosphonate of the type,

With R¹ an alkyl group of carbon length 1-32, and n>1

EXAMPLE 4 Preparation of Nanoalloy Particle Flame Modulation AdditiveConcentrate

Mn(NO₃)₂+Na₂H₂Sb₂O₇.7H₂O→MnSb₂O₆

MnSb₂O₆+-nR(X)_(m)→MnSb₂O₆.[—R(X)_(m)]_(n), where;

R(X)_(m) is a diaryl alkyl- or aryl-phosphonate of the type:

With R¹ an alkyl group of carbon length 1-32, m=Br=5, and n>1

EXAMPLE 5 Preparation of Nanoparticles with Ammonia and/or Alkyl- and/orAry-Amines

MnVSbO₆+-nR(X)_(m)→MnVSbO₆.[-nR(X)_(m)]_(n), where;

Where R(X)_(m) is alkyl- and/or aryl-amines of the type:

And PIB is a low molecular weight polyisobutylene group

EXAMPLE 6

NaSbO₃+Fe(NO₃)₃+Mn(NO₃)₂→FeMnSbO₄

FeMnSbO₄+-nR(X)_(m)→FeMnSbO₄[—R(X)_(m)]_(n), where,

R(X)_(m) is a polyhalogenated alky- and/or ary-halide such as:

And R¹ is an alkyl group of carbon length from 1-32 carbon atoms.

EXAMPLE 7

Al(OH)₃+(NH₄)₄Mo₈O₂₆→Al(OH)₃.[(NH₄)₄Mo₈O₂₆]

Al(OH)₃.[(NH₄)₄Mo₈O₂₆]+-nR(X)_(m)→Al(OH)₃.[(NH₄)₄Mo₈O₂₆].[—R(X)_(m)]_(n),where,

R(X)_(m) is an alkly- or aryl-phosphorus-derived oxide of the type:

And R¹ is an alkyl group of carbon length from 1-32 carbon atoms.

EXAMPLE 8 Fuel Additization Methods

In general, propellant fuels are of three major classes:

Cryogenics, i.e. hydrogen (H₂), hydrazine (N₂H₄), ammonia (NH₃), etc.;

Storables, i.e. Acetylene (C₂H₂), aluminum borohydride (AlBH₄), ammonia(NH₃), aniline (C6H7N), Biborane (B₂H₄), Ethanol (C₂H₆O), furfurylalcohol, kerosene, pentaborane, unsymmetrical dimethyl hydrazine((CH₃)₂NNH₂ or UDMH), ethylene oxide, hydrogen peroxide, nitromethane,propyl nitrate, and etc. The latter four are known as “monopropellents”because they carry some of the oxidizer necessary for combustion; and

Solids, i.e. NH₄ClO₄-Polyurethane, NH₄ClO₄-Organo-boron, ammoniumnitrate, epoxy plastics, nitrocellulose plastics, polyester plastics,nitroglycerin,

Cryogenics can enter the combustion zone as gases; therefore theappropriate flame modulation additive would have to be injectedseparately.

Storables are either liquids or solids that do not require extraordinarymeasures during handling, storage and use. When liquids, the combustionmodulation additive would be dispersed in the fuel by selecting theappropriate length R-group on —R(X)_(m) ligand coating thenanoparticle/nanoalloy additive core.

When the fuel is a solid or gel, then the additive needs to be mixed induring the fuel synthesis process at stages where the steps go through aliquid phase, and no further reactive steps follow that may alter theintended performance of the additive.

In one embodiment, a fuel additive comprising a nanoparticle matrixcomprising oxides, and/or hydroxides, and/or hydrates of one or more ofthe following elements Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi, Ca, Na, K, Ba,Bi, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V is blended at a treat of 500ppm of fuel additive nanoparticle matrix with non-nitrated cellulosepre-fuel at ambient temperatures. The resulting additized pre-fuelmixture is then nitrated using known reaction parameters and conditionsresulting in a solid fuel containing a nanoparticles matrix, wherein thecombustion rate of the cellulose fuel has been modulated relative to thecombustion rate of nitrated cellulose.

In another embodiment, a fuel additive comprising a nanoparticle matrixcomprising oxides, and/or hydroxides, and/or hydrates of one or more ofcombinations selected from the group consisting of Na/B, Zn/B, Na/Sb,and Fe/Mn is blended at a treat rate of 100 ppm of fuel additivenanoparticle matrix with non-nitrated cellulose pre-fuel at ambienttemperatures. The resulting additized pre-fuel mixture is then nitratedusing known reaction parameters and conditions resulting in a solid fuelcontaining a nanoparticles matrix, wherein the combustion rate has beenmodulated relative to the combustion rate of nitrated cellulose.

EXAMPLE 9 Testing Procedure

The solid test fuel is characterized in the pertinent combustionenvironment and the oxidation reaction rates determined. This providesthe key baseline parameter for ranking the combustion modulation effectof the additive formulations.

Additives i)-ii) are formulated into the solid fuel. First additives i)and then additives ii) will be formulated into chosen solid fuel at 100ppm wt/wt total metal.

Combustion rates of the fuels will be carried out and selection ofadditives for specific desired applications made.

Best additives from i) and ii) will be modified as shown in iv) throughx), respectively and formulated into the respective solid fuel. Reactionrates are then determined as above.

At numerous places throughout this specification, reference has beenmade to a number of U.S. patents, published foreign patent applicationsand published technical papers. All such cited documents are expresslyincorporated in full into this disclosure as if fully set forth herein.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the present disclosure. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” include plural referents unlessexpressly and unequivocally limited to one referent. Thus, for example,reference to “an antioxidant” includes two or more differentantioxidants. As used herein, the term “include” and its grammaticalvariants are intended to be non-limiting, such that recitation of itemsin a list is not to the exclusion of other like items that can besubstituted or added to the listed items.

This invention is susceptible to considerable variation in its practice.Therefore the foregoing description is not intended to limit, and shouldnot be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

Applicant does not intend to dedicate any disclosed embodiments to thepublic, and to the extent any disclosed modifications or alterations maynot literally fall within the scope of the claims, they are consideredto be part of the invention under the doctrine of equivalents.

1. A fuel additive comprising at least one of: i) a particle(s) ornanoparticle(s) of oxide(s), hydroxide(s), hydrate(s), and/orcarbonate(s) selected from the group consisting of: Al, Sb, Mg, Fe, Mo,Zn, Sn, B, Bi, Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce,and V; and ii) an alloy(s) or nanoalloy(s) containing two or more metalsselected from the group consisting of Al, Sb, Mg, Fe, Mo, Zn, Sn, B, Bi,Ca, Li, Na, K, Ba, Mn, Si, Cu, Cd, Co, Ni, Cr, Ti, Ce, and V; wherein atleast one of the i) particles or nanoparticles and ii) alloys ornanoalloys can be capped with at least one iii) flame retardantmaterial.
 2. The additive of claim 1, wherein the average size of theparticle or alloy is from about 1 to about 100 nanometers.
 3. Theadditive of claim 1, wherein the average size of the particle or alloyis from about 5 to about 75 nanometers.
 4. The additive of claim 1,wherein the flame retardant material can be selected from the groupconsisting of polyhalogenated alkyl halides, polyhalogenated arylhalides, alkyl phosphorus-derived oxides, aryl-phosphorus-derivedoxides, ammonia, alkyl amines, and aryl amines.
 5. The additive of claim1, wherein the i) hydroxide is Mg(OH)₂ or Ti(OH)₂.
 6. The additive ofclaim 1, wherein the i) metal oxide is selected from the groupconsisting of Sb₂O₃, SnO₂, ZnO, MoO₃, Fe₂O₃, CoO, and (NH₄)₄Mo₈O₂₆. 7.The additive of claim 1, wherein the i) hydrate is Al₂O₃.3H₂O orAl(OH)₃(H₂O)_(x).
 8. The additive of claim 1, wherein the i) carbonateis CaCO₃ or MgCO₃.
 9. The additive of claim 1, wherein the alloy isselected from the group consisting of Al/Sb, Na/B, Zn/B, Na/Sb, Fe/Mn,Ba(BO₂)₂, LiB₃O₅, 2ZnO.3H₂BO₃.3.5H₂O, Na₂B₄O₇.10H₂O, Na₃SbO₄, LnSbO₄,SiSbO₄, FeSbO₄, TiSbO₄, CeSbO₄, VSbO₄, VMoSbO₄, MnVSbO₆, CaMnSb₄O₁₄,BaSbO₅, Ca₂O.SbO₅, and Co₂O.Sb₂O₅, Mg₂O.Sb₂O₄.
 10. The additive of claim1, wherein the alloy can be represented by the following generic formula(Aa)n(Bb)n(Cc)n(Dd)n(Ee)n( . . . )n; wherein each capital letter and ( .. . ) is a metal described hereinabove; wherein each n is independentlygreater than or equal to zero; and wherein the alloy comprises at leasttwo different metals.
 11. The additive of claim 1, wherein the fueladditive is further capped with an organic capping ligand with a polarheteroatom-derived functionality.
 12. A fuel composition comprising afuel and a fuel additive of claim
 1. 13. The fuel composition of claim12, wherein a treat rate of the fuel additive is from about 5 ppm toabout 25,000 ppm of fuel.
 14. The fuel composition of claim 12, whereina treat rate of the fuel additive is from about 5ppm to about 500 ppm.15. The fuel composition of claim 12, wherein a treat rate of the fueladditive is from about 100 ppm to about 500 ppm of solid fuel.
 16. Amethod of modulating fuel combustion by producing fuel dilution bygeneration of non-combustible gases selected from the group consistingof N₂, H₂O, CO₂, HX, and SO₃ said method comprising: a) combining a fueland a fuel additive of claim 1 to form a mixture, wherein the additivecomprises a material capable of generating, when heated, anon-combustible gas selected from the group consisting of N₂, H₂O, CO₂,HX, and SO₃; b) combusting the mixture, thereby generating saidnon-combustible gas, whereby the fuel in said mixture is diluted.
 17. Amethod of modulating fuel combustion by producing cooling endothermicreactions, the method comprising: combusting a mixture of fuel and fueladditive of claim 1, whereby the fuel additive when heated enters anendothermic reaction, whereby cooling of the fuel combustion occurs. 18.A method of modulating fuel combustion by forming a protective layer ona solid fuel, said method comprising: a) combining a solid fuel and afuel additive of claim 1 to form a mixture, b) heating the mixture to atemperature at least sufficient to cause the additive to form aprotective glassy layer on the mixture, whereby the fuel combustion ismodulated.
 19. A method of modulating fuel combustion by condensed phaseactivity, said method comprising: combusting a mixture of fuel and fueladditive of claim 1, whereby the fuel additive when heated induces phaseactivity, whereby the fuel combustion is modulated.
 20. The method ofclaim 19, wherein the activity comprises one or more of the actionsselected from the group consisting of charring and cross-linking.
 21. Amethod of smoke suppression by condensed phase activity, said methodcomprising: combusting a mixture of fuel and fuel additive of claim 1,whereby the fuel additive when heated induces phase activity wherebygeneration of smoke from said combustion is suppressed.
 22. A method ofmodulating fuel combustion by vapor or gas phase activity, said methodcomprising: combusting a mixture of fuel and fuel additive of claim 1,whereby the fuel additive when heated induces phase activity, wherebythe fuel combustion is modulated.
 23. The method of claim 22, whereinthe gas in the gas phase is selected from the group consisting of HX,HX/Sb, and P, wherein X is a halogen.
 24. A combustion system comprisinga system for combusting fuel and a fuel additive of claim 1.